1. Field of the Invention
The present invention is directed to an optical wavelength division coupler, more particularly to an integrated coupler, and a method of making the same.
2. Description of Related Art
Optical multipexers/demultiplexers are generally known in the art. See, for example, commonly assigned U.S. Pat. No. 6,684,010, which is hereby incorporated by reference for all purposes. FIG. 1 is a schematic cross-section of the multiplexer of an embodiment of the '010 patent present invention. An array 104 of light sources 104a-104d, here shown as vertical cavity surface emitting lasers (VCSELs), is provided on a substrate 102. Light output by the light source array 104 is directed to a first optics block 110 having a corresponding plurality of collimating/deflecting elements 112. The light source array 104 is separated from the first optics block 110 by a spacer 106, here shown as etched silicon. The collimated/deflected light then hits a corresponding plurality of filters 122, one for each appropriate wavelength of light. The filters 122 are preferably mounted on or formed on a second optics block 120, but may be provided on a separate, intermediate optics block.
The light passing through the filters 122 is directed to an opposite surface of the optics block 120 having a reflective element 124 thereon. In this particular configuration, the opposite side of the optics block 120 also has a focusing/deflecting element 126 thereon for focusing the light onto a fiber 130, which, as shown in FIG. 1, may be housed in a fiber receptacle 132 or other fiber mount. Alternatively, the fiber could be in a connector located externally to the module in a connector such as an MT-RJ, MTP or LC. The light reflected by the reflective element 124 is directed back toward the input surface of the optics block 120 where it is incident on another filter of the plurality of filters 122. Since each filter will only pass light of a particular wavelength and the light source array 104 has light sources of different wavelengths, all of the filters other than the corresponding filter at the output of the light source will reflect the light back toward the other surface of the optics block 120. Each corresponding filter allows the light from the corresponding light source to pass therethrough to thereby enter the optics block 120.
If this configuration is exploded to view the constituent elements thereof, as shown in FIG. 2, it can be appreciated that there are six (6) parallel surfaces out of which the coupler is constructed, i.e., surfaces 10, 20, 30, 40, 50, 60. When mounting discrete filters 112a-112d, any particle, e.g., dust, between the filter and a surface it is secured to may result in a tilt, changing the location of the output beam on the fiber or the input beam on the detectors. When dealing with filters on the order of 400 microns wide, even a 0.2 micron particle can result in a tilt of greater than 1 arc-min.